Anyone wondering about the level of interest in the HTML5 specification need only have tried to get into a standing room-only session on the topic at Google's developer conference on Wednesday afternoon.

An estimated 450 to 500 persons were able to get into the session, entitled "Developing With HTML5," at the Google I/O conference in San Francisco. Outside the room, many others were turned away.

HTML5 has been at the heart of an ongoing debate over whether proprietary rich Internet plug-in technologies such as Adobe's Flash could be rendered obsolete by HTML5.

"We're interested in HTML5 because it's the future of the Web, and even Microsoft supports it to some extent even though it's slightly different in their browser," said conference attendee and Web developer Peter Svensson, who could not gain entry into the session.

Another attendee who was denied entrance also had high hopes for HTML5.

"I think it's definitely the way things are heading," said James Moore, CTO at Mibbit, which makes a rich Web chat client that leverages the specification.

Earlier in the day during a panel session held for press, Google officials saw Flash as still having a technical advantage in terms of delivering animation and graphics.

"We're making enormous progress. Flash has been at this and Adobe's been at this for many years," said Linus Upson, Google vice president of engineering.

"We have our work cut out for us" in making HTML5 better than Flash, Upson said. But he did not think it would take very long to accomplish this.

"Flash solves a lot of problems today which HTML5 cannot," said Sundar Pichai, Google vice president of product management. "We see [HTML5 and Flash] co-existing."

"We want to see HTML5 get better," Pichai said.

Flash, for example, offers advantages in areas such as secure streaming of premium content, Pichai said.